Most United Methodist clergy do not wear the clergy collar or shirt, although many have both items. Many of our clergy would never — under any circumstances wear a collar — probably because they feel the collar would "put off" the laity or because they resist any association with "priestly" images. Some would wear the collar in very formal, ecclesiastical settings or in hospital or social witness situations, where being identified as an ordained person could be helpful. There are a small number of clergy who wear the shirt "to bed" — meaning, they wear the collar almost all the time when they are on duty. There are good arguments for not wearing and for wearing the collar. United Methodist clergy are free to choose whether or not to wear the collar.
The full collar is a white plastic band that attaches to the shirt with chrome collar buttons. The more comfortable tab shirt has a plastic strip inserted into both sides of the shirt collar.
These days, many shirt colors are available from church supply houses, although black is the "standard" color for the working pastor. Purple or maroon is reserved for bishops, and these colors should not be worn by other clergy.
In the United Methodist Church, we have licensed local pastors who are considered clergy, although they are not ordained. It is appropriate for these pastors to wear the collar in carrying out their pastoral duties. However, I suspect that few of them do.